Telephone-transmission system



Sept. 9 1924.

v D. F. WHITING TELEPHONE TRANSMISSION SYSTEM Filed Jan. 10, 1920 hove/Mar: Dona/d F. Wh/f/nq Afiy.

Patented Sept. 9, 1924.

UNITED STATES PATENT OFFICE.

DONALD F. WHITING, OF NEW YORK, N. Y.. ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N Y., A CORPORATION OF NEW YORK.

TELEPHONE-TRANSMISSION SYSTEM.

Application filed January 10, 1920. Serial No. 350,526.

To all whom it may concern:

Be it known that I, DONALD F. lVHI-TING, a citizen of the United States, residing at New York, in the county of Bronx and State of New York, have invented certain new and useful Improvements in Telephone-Transmission Systems,of which the following is a full, clear, concise, and exact description.

This invention relates to transmission systems, and more particularly to a transmission line or lines designed for the efficient transmission of currents of frequencies within a desired range, and so organized that they will also be highly efiicient for the transmission of currents of frequencies outside the desired range. Such a system may comprise a transmission line over which is transmitted both telephonic and signaling currents, the line being designed primarily for the efficient transmission of currents within the telephonic range of frequencies but so adapted that it may be rendered temporarily eflicient for the transmission of Sig naling currents of much lower frequencies@ In-Wilbur-Bendernagel Patent 1,371,717,

Mar. 15, 1921, and in \Vhiting Patent 1,471,638, Oct. 23, 1923, transmission'lines are disclosed which are provided with am pliiiers for rendering the transmission of telephonic currents over the transmission lines efficient, and also with ringing response relays which, upon response to ringing current transmitted thereto, so alter the input circuits of the amplifiers as to regulate the gain or amplification of the amplifiers for the purpose of effecting a more eflicient transmission of the signaling or ringing currents.

Normally, the electrical characteristics of the transmission line and of the amplifying circuits associated therewith are so selected that currents within the telephonic range of frequencies are transmitted without appreciable attenuation, and therefore it follows that when ringing current of much lower frequency, for example of 135 cycles 1 is transmitted, the electrical characteristics of the system are no longer suitable for efficient transmission and very little energy is transmitted through the amplifiers to the ringing response relay which is connected into the output circuit of the final amplifier. In order that the response relay may operate upon the small energy which it receives, it

is necessary to give the relay a very sensitive adjustment. This sensitive adjustment is not only difficult to obtain but is exceedingly difficult to maintain properly when secured, since the relay is not only subject to electrical abuse, but because of its sensitivity its adjustment is adversely affected by the vibration of the exchange building within which it is installed.

It is a purpose of this invention to obviate this difficulty by providing a less sensitive response relay and transmit to it nearly the entire output energy of the amplifier at the ringing frequency. Since, however, the relay following its initial operation causes substantially a fifteen fold increase of amplification of the amplifiers, this would lead to a diversion of substantiall the entire output energy of the ampli ers through the winding of the relay, leaving a relatively small amount of energy available for transmission out over the transmission line to the next amplifying station, and to an overloading of the relay, causing thereby a disar rangement of its delicate mechanical adjustment. A decrease in the quantity of energy supplied to maintain the relay energized during the period following its initial operation and until the incoming ringing current ceases, is necessary to prevent the abuse of the relay, and at the same time render a greater amount of the amplified ringing or signaling energy available for transmission out over the transmission line to a subsequent amplifying station.

An investigation of the impedance relations of the response relay and the output circuit of the amplifier in which it is connected, has demonstrated that by increasing the impedance of the circuit-in which the response relay is connected until it is comparable to the impedance of the remaining portions of the amplifier output circuit, the response relay initially receives a greater amount of energy. By this increase of energy, however, the major portion of the 1 output energy derived from the amplifiers is diverted into the relay, so that little remains to be transmitted out over the transmission line. This condition may be avoided if changes are made in the circuit connections of the response'relay subsequent to its operation, and at the time it functions to increase the amplification of the signaling current.

The principal object of the present invention is the provision of means for securing the most efficient transmission of signaling current by initially transmitting sufiicient energy to positively operate the signaling response relay, and maintaining the amount of energy transmitted to the .relay substantially constant throughout the duration of the signaling period.

In attaining this object of the invention, there is associated with each amplifying station on a transmission line, an electro-responsive device, responsive to ringing or signaling currents but not responsive to telephonic or voice currents- This ringing response device, upon responding, controls through certain switching devices the connection of means into the input circuit of the amplifying station, whereby the station is transformed temporarily from one highly eflicient for the transmission ofvoice or telephonic currents to one highly efficient for the transmission of ringing or signaling currents, and the alteration of its own connection to the output circuit.

A further object of the invention is to provide means for reducing the transmission loss incident to the coupling of the high impedance output circuit of the vacuum tube amplifier to the low impedance circuit of the ringing response relay.

For a more complete understanding ofthe invention, reference should be made to the following description considered in connection with the accompanying drawing illustrating certain embodiments of the invention, in which:

Figure 1 shows one amplifying station of a transmission line equipped with improved circuits in accordance with this invention; and

Figure 2 shows a further embodiment of the invention.

Referring first to Fig. 1, one amplifying station of a transmission line is disclosed. L represents the incoming section of the transmission line which is inductively connected to the section L, by a transformer or repeating coil 5. Section L is connected to the outgoing section L of the transmission line through an input repeating coil 6, a twostage amplifier set comprising amplifiers 7 and 8, the outputcircuit of the former being connected with the input circuit of the latter,

and an output repeating coil 9. Between the secondary winding of repeating coil 5 and the primary winding of coil 6, there is connected a potentiometer 10, and between the output circuit of amplifier 7 and the input circuit of amplifier 8, there is a second potentiometer 11, these potentiometers being arranged to regulate the input energy applied to the two amplifiers. A condenser 12 i is also arranged to be connected across the section L of the transmission line between the potentiometer 10 and the primary winding of coil 6 for controlling the gain or amplification of the amplifier 7.

In the output circuit of the amplifier 8, there is connected a ringing response relay 13 which, through a switching relay 14, controls the connection of condenser 12 across section L and'the relation of the response relay 13 to the output circuit of amplifier 8. Normally, response relay 13 is in a deenergized condition and maintains the switching relay 14 energized over a circuit extending through its armature and back contact. At its left-hand armature contacts, relay 14 thus maintains the condenser 12 disconnected from section L and at the make contacts of its ri ht-hand armature connects the winding 0' response relay 13 in a circuit in series with the primary windings of repeating coil 9. The circuit of relay 13 may be traced from the plate element of amplifier 8, through the upper primary winding of repeating coil 9, condenser 15, make contacts of relay 14, winding of relay 13, retardation coil 18,. the lower primary winding of coil 9 and thence to the filament element of the amplifier. The circuit traced above branches at the winding of relay 13 and extends through the condensers l6 and 17 in such manner that the condensers are connected in parallel to that portion of the circuit above traced including retardation coil 18 and the winding of relay 13.

The output circuit of amplifier including the primary windings of coil 9 has a com paratively high impedance of approximately 9,000 ohms, whereas the response relay 13 has a low impedance of about 700 ohms. The coupling of these circuits as now employed leads to a transmission loss which at the ringing frequency has been experimentally determined to amount to substantially 8.7 miles. It is therefore preferable to increase the impedance of the circuit of relay 13 to a value substantially equal to the impedance of the output circuit of the amplifier, whereby the transmission loss is reduced to about .6 miles. This is accomplished by the rovision of condenser 16 and retardation coil 18 which have impedance characteristics of the proper value. While the coil 18 is shown as connected in series with the winding of relay 13, and the condenser 16 as bridged across the terminals of the circuit of relay 13, the position of these elements might be reversed and function in the same manner to reduce the transmission loss. It is further obvious that while the circuits disclosed for reducing the transmission loss have been'shown as associated with a telephone repeater system, they are of much broader application and might be utilized in other associations.

Upon the application of 135 cycle ringing or signaling current, relay 13 receives sufficient energy to cause it to energize, thereby openin the circuit of relay 1 1 which thereupon eenergizes. Relay 14 upon deenergizing closes its left-hand armature contacts, thereby bridging the condenser 12 across the section L of the transmission line to cause the gain of increase in amplification or amplifier 7, and at its right-hand armature contacts opens the initial energizing circuit of relay 13 and reconnects the relay into the output circuit in such manner that the relay receives only sufiicient current through its winding to maintain it energized through the continuance of the ringing current. The energizing circuit of relay 13 may now be traced from the plate of amplifier 8 through the upper primary winding of repeater coil 9, condenser 15, condenser 16, winding of relay 13, retardation coil 18, the lower primary winding of coil 9 and thence to the filament element of the amplifier. The condenser 16 now reduces the effective inductance of the circuit includin the condenser 16, rela 13 and retardation coil 18 while not diminishinrr the efi'ective resistance of the circuit. The condenser 17 whichis now connected in parallel with that portion of the circuit of relay 13 including the condenser 16, relay 13 and retardation coil 18 forms an anti-resonant circuit therewith which is also tuned to the ringing frequency, a circuit however of much lower impedance than the circuit to which it is joined. Relay 13 is thus connected into an anti-resonant circuit and now receives substantially the same amount of energy as it did upon its initial energization, although the amount of energy transmitted into the output circuit is approximately fifteen times as great. Thus relay 13 is not over-loaded or electrically abused following the amplification of the ringing current, while substantially the whole of the amplified energy is available for transmission into the outgoing section L of the transmission line.

In Fig. 2, a further embodiment of. the invention is disclosed which is so organized that a greater degree of decrease in the impedance of the circuit containing the response relay during the ringing period is attained than with the circuit disclosed in Fig. 1. In general the circuits shown in Fig. 2 are the same as those in Fig. 1, differing therefrom only in the manner in which the response relay is associated with the output circuit prior to and subsequent to its response.

In this embodiment a double-Wound response relay 19 is employed which is initially connected into the output circuit over a path which may be traced from the plate element of amplifier 8 through the upper primary winding of repeating coil 9, condenser 15, the normally closed make contacts of the intermediate armature of relay 20, the

retardation coil 21, the left-hand winding of response relay 19, the normally closed make contacts of the upper armature of relay 20, the right-hand winding of relay 19, the lower primary winding of repeating coil 9, and thence to the filament element of the amplifier 8. A branch circuit bridging retardation coil 21 and the winding of relay 19 is also closed at this time extending from the normally closed contacts of the lower armature of relay 20, through condenser 17, the lower primary winding of coil 9 and thence to the filament of the amplifier. Upon the response of relay 19 to the initial flow ofringlng current, relay 2O deenergizes and closes at its lowermost armature contacts a circuit forbridging condenser 12 across section L of the transmission line, and at its intermediate and uppermost armature contacts alters the connection of response relay 19 to the output circuit in such a manner that the windings of relay 19 are changed from a serial connection to a parallel connection with res ect to the output circuit.

The maintaining circuit of relay 19 may now be traced from the plate element of amplifier 8 through the upper primary winding of repeating coil 9, condenser 15, the intermediate armature and back contact of relay 20, condenser 22, in parallel through the two windings of coil 19 to lower primar winding of repeating coil 9, and thence to tie filament element of the amplifier 8. Through this alternation ofthe connection of relay 19, the relay receives only so much of the amplified ringing current as is neces sary to maintain its energizationduring the application of the ringing current.

From the foregoing description, it is believed that it will be apparent to those skilled in the art that provision has been made for supplying sufiicient initial energizing current to the response relays to permit them to operate without being as delicately ad'usted as heretofore, and for-maintaining t e energy supplied to such rela s substantially constant before and after t e response of the relays, thus eliminating the abuse due to overloading to which they were previously subject, and allowing nearly the entire output energy of the amplifiers to be available for transmission over the succeedin line section.

Vhat is claimed is:

1. In a transmission system, an amplifying repeater, means for supplying signals to said repeater, means for increasing the amplification of said repeater and for altering the characteristics of the output circuit, and means in the output circuit of said repeater and responsive to incoming signals for controlling said last named means.

2. In a transmission system, an amplifying repeater, a. responsive means in the output circuit of said repeater, means under the control of said responsive means for increasing the amplification of said repeater, and

means controlled by said responsive means for maintaining the energy absorbed by said responsive means at the same value prior to and subsequent to said increase of amplification.

3. In a transmission system, an amplify ing repeater, a responsive means in the output circuit of said repeater, a relay under the control of said responsive means for increasing the amplification of said re peater, and means also under the control of said relay for altering the impedance characteristics of said output circuit, whereby said responsive-means receives substantially the same amount of energy both prior to and subsequent to its operation.

4. In a transmission system, an amplifying repeater, a double wound response relay in the output circuit of said repeater, means under the control of said response relay for increasing the amplification of said repeater and for changing the windings of said relay from a series to a parallel connection in said output circuit, whereby the said relay receives substantially the same amount of energy both prior to and subsequent to its operation.

5. In a transmission system, an amplifying repeater, a response relay, an initial energizing circuit for said relay comprising a retardation coil and the Winding of said response relay in serial relation in the output circuit of said repeater, a condenser in parallel with said retardation coil and said response relay, and means under the control of said response relay for reconnecting its winding in series with said condenser into said output circuit.

6. In a transmission system, an amplifying repeater, a double wound responserelay, an initial energizin circuit for said rela comprising a retar a-tion coil and both wlndings of said relay in serial relation in the output circuit of said repeater, a condenser in parallel with said retardation coil and response relay, and means under the control of said response relay for re-connecting its windings in parallel with each other and inseries with said condenser into said output circuit.

7. In combination, a vacuum tube, a translating device, means for supplying energy to said device tending to be dependent in value upon a characteristic of said tube. means for changing a characteristic of said tube, and means controlled by said last means for causing said device to absorb substantially the same amount of energy as it did previous to said change.

8. In a transmission system, an amplifying repeater having an output circuit, an outgoing transmission line coupled to said output circuit, means for supplying signals to said repeater. means in said output circuit responsive to said signals, and means controlled by said second means for increasing the amplification of said repeater for said signals and for modifying said output circuit to secure an elficient transmission of said signals to said outgoing line.

In witness whereof, I hereunto subscribe my name this 7th day of January A. D.,

DONALD F. WHITING. v 

